The seat of automotive seats and office chairs is composed of a cushion made of a foamed urethane, etc. and a seat cover (upholstery material) covering the surface of cushion.
In the production of automotive seats, a so-called mold-in process is used, wherein a fastening member having a number of engaging elements on its top surface and a number of anchoring elements on its back surface is placed in the desired position of a mold; and a molding resin (foamable liquid resin) is injected into the mold and allowed to foam so that the anchoring elements are embedded in the resulting molded article of foamed resin, thereby uniting the molded article of foamed resin and the fastening member while allowing the fastening member to be embedded in the surface of the molded article of foamed resin such that the engaging elements are exposed on the outer surface of the molded article of foamed resin.
The seat cover (upholstery material) has on its back surface the engaging elements which cooperate with the engaging elements of the fastening member. By joining the cooperating engaging elements with the engaging elements on the surface of the molded article of foamed resin, the seat cover is fixed to the molded article of foamed resin along its surface.
Formerly, a hard fastening member having hook engaging elements (hereinafter may be referred to as “hook member”) has been used as the fastening member to be placed in the mold because of its easiness of handling. In the method of using the hook member, the back surface thereof is embedded in a resin molded article so as to expose the hook engaging elements on the surface thereof, and the exposed hook engaging elements are joined with the loop engaging elements foamed on an upholstery material (for example, Patent Document 1).
In the mold-in process mentioned above, generally, the fastening member is placed into a narrow recess which is formed at a given position of a mold while allowing its surface having hook engaging elements to face the bottom of the recess and then a foamable liquid molding resin is injected into the mold while keeping the fastening member in position to perform the molding. In conducting the mold-in process with the fastening member fitted to the recess, the introduced liquid resin enters into the side of engaging elements through gaps between the fastening member and the recess, thereby encasing the engaging elements in the foamed resin. Since the engaging elements surrounded by the resin no longer have the engaging function, the liquid resin should be prevented from entering into the mold in the mold-in process so as to prevent the surface having engaging elements from being encased in the resin.
Recently, the structure and design of seat come to be complicated and widely range, and therefore, the molded article of foamed resin for seats is needed to change its shape from a flat plate shape to a two-dimensional shape and further to a three-dimensionally curved shape. However, in the technique of incorporating the known hard hook member into the molded article of foamed resin, it is very difficult to bend the hook member three-dimensionally (bend the hook member roundly) and to produce a molded article while preventing the surface having engaging elements from being surrounded by the resin. For example, a known hard hook member is hardly bent sideways in nearly parallel to the hook surface, i.e., hardly bent in plane because of its poor elasticity. Therefore, it is quite difficult to fit the fastening member into the recess in a mold by bending it roundly so as to follow the three-dimensionally curved recess. If the fastening member is forcedly bent, it bends with kink. Alternatively, the inner side and the outer side at the bend portion do not lie on the same plane, and therefore, the outer side or the inner side rises from the recess and a foamable liquid molding resin flows into the recess from the rising portion to make the surface having engaging elements encased in the foamed molding resin.
As described above, it is very difficult to bend a known fastening member roundly so as to conform to the three-dimensionally curved surface. If it is forcedly bent, gaps which allow the foamable liquid molding resin to enter into the recess are left between the hard fastening member and the recess formed in the mold. As a result, the hook surface of the fastening member is covered by the foamed molding resin and the hook elements lose the engaging function because the foamed molding resin covering the fastening member is difficult to remove.
To avoid the problem caused by bending the hook member three-dimensionally, Patent Document 2 proposes to reduce the apparent rigidity of the hook fastening member to make the in-plane deformation easy by providing at least one ridge for controlling deformation on the back side of substrate (surface opposite to hook engaging elements). The proposed method is somewhat effective when the fastening member is slightly deformed in plane or the substrate of fastening member has a narrow width. However, the problem of the surface of engaging elements to be covered by the foamed molding resin is not solved so greatly and the proposed method is not so effective if the in-plane deformation is large and the width of substrate is large.
Patent Document 1: JP 5-016173A
Patent Document 2: JP 2006-122269A